video: make it possible to scale/pan the video by arbitrary amounts

Add --video-align-x/y, --video-pan-x/y, --video-scale options and
properties. See the additions to the manpage for description and
semantics.

These transformations are intentionally done on top of panscan. Unlike
the (now removed) --panscanrange option, this doesn't affect the default
panscan behavior. (Although panscan itself becomes kind of useless if
the new options are used.)

6 files changed, 62 insertions, 5 deletions

diff --git a/DOCS/man/en/input.rst b/DOCS/man/en/input.rst
index ae887a2080..bacb99c14b 100644
--- a/DOCS/man/en/input.rst
+++ b/DOCS/man/en/input.rst
@@ -452,6 +452,11 @@ Name                            W Comment
 ``aspect``                      x video aspect
 ``vid``                         x current video track (similar to ``--vid``)
 ``video``                       x alias for ``vid``
+``video-align-x``               x see ``--video-align-x``
+``video-align-y``               x see ``--video-align-y``
+``video-pan-x``                 x see ``--video-pan-x``
+``video-pan-y``                 x see ``--video-pan-y``
+``video-zoom``                  x see ``--video-zoom``
 ``program``                     x switch TS program (write-only)
 ``sid``                         x current subtitle track (similar to ``--sid``)
 ``sub``                         x alias for ``sid``
diff --git a/DOCS/man/en/options.rst b/DOCS/man/en/options.rst
index 210f89381b..4174e1f0d6 100644
--- a/DOCS/man/en/options.rst
+++ b/DOCS/man/en/options.rst
@@ -2458,6 +2458,39 @@
 ``--vid=<ID|auto|no>``
     Select video channel. ``auto`` selects the default, ``no`` disables video.
 
+``--video-align-x=<-1-1>``, ``--video-align-y=<-1-1>``
+    Moves the video rectangle within the black borders, which are usually added
+    to pad the video to screen if video and screen aspect ratios are different.
+    ``--video-align-y=-1`` would move the video to the top of the screen
+    (leaving a border only on the bottom), a value of ``0`` centers it
+    (default), and a value of ``-1`` would put the video at the bottom of the
+    screen.
+
+    If video and screen aspect match perfectly, these options do nothing.
+
+    This option is disabled if the ``--no-keepaspect`` option is used.
+
+``--video-pan-x=<value>``, ``--video-pan-y=<value>``
+    Moves the displayed video rectangle by the given value in the X or Y
+    direction. The unit is in fractions of the size of the scaled video (the
+    full size, even if parts of the video are not visible due to panscan or
+    other options).
+
+    For example, displaying a 1280x720 video fullscreen on a 1680x1050 screen
+    with ``--video-pan-x=-0.1`` would move the video 168 pixels to the left
+    (making 128 pixels of the source video invisible).
+
+    This option is disabled if the ``--no-keepaspect`` option is used.
+
+``--video-zoom=<value>``
+    Adjust the video display scale factor by the given value. The unit is in
+    fractions of original video size.
+
+    For example, given a 1280x720 video, ``--video-zoom=-0.1`` would make the
+    video by 128 pixels smaller in X direction, and 72 pixels in Y direction.
+
+    This option is disabled if the ``--no-keepaspect`` option is used.
+
 ``--vo=<driver1[:suboption1[=value]:...],driver2,...[,]>``
     Specify a priority list of video output drivers to be used. For
     interactive use, one would normally specify a single one to use, but in
diff --git a/mpvcore/command.c b/mpvcore/command.c
index b7aa9dfe6a..ae3f97a5bc 100644
--- a/mpvcore/command.c
+++ b/mpvcore/command.c
@@ -1253,9 +1253,9 @@ static int mp_property_colormatrix_output_range(m_option_t *prop, int action,
     return M_PROPERTY_OK;
 }
 
-/// Panscan (RW)
-static int mp_property_panscan(m_option_t *prop, int action, void *arg,
-                               MPContext *mpctx)
+// Update options which are managed through VOCTRL_GET/SET_PANSCAN.
+static int panscan_property_helper(m_option_t *prop, int action, void *arg,
+                                   MPContext *mpctx)
 {
 
     if (!mpctx->video_out
@@ -1809,7 +1809,12 @@ static const m_option_t mp_properties[] = {
                     .offset = offsetof(struct MPOpts, gamma_saturation)),
     M_OPTION_PROPERTY_CUSTOM_("hue", mp_property_gamma,
                     .offset = offsetof(struct MPOpts, gamma_hue)),
-    M_OPTION_PROPERTY_CUSTOM("panscan", mp_property_panscan),
+    M_OPTION_PROPERTY_CUSTOM("panscan", panscan_property_helper),
+    M_OPTION_PROPERTY_CUSTOM("video-zoom", panscan_property_helper),
+    M_OPTION_PROPERTY_CUSTOM("video-align-x", panscan_property_helper),
+    M_OPTION_PROPERTY_CUSTOM("video-align-y", panscan_property_helper),
+    M_OPTION_PROPERTY_CUSTOM("video-pan-x", panscan_property_helper),
+    M_OPTION_PROPERTY_CUSTOM("video-pan-y", panscan_property_helper),
     { "video-format", mp_property_video_format, CONF_TYPE_STRING,
       0, 0, 0, NULL },
     { "video-codec", mp_property_video_codec, CONF_TYPE_STRING,
diff --git a/mpvcore/options.c b/mpvcore/options.c
index 5600ccee71..5aff219c14 100644
--- a/mpvcore/options.c
+++ b/mpvcore/options.c
@@ -581,6 +581,11 @@ const m_option_t mp_opts[] = {
     OPT_INTRANGE("fsmode-dontuse", vo.fsmode, 0, 31, 4096),
     OPT_FLAG("native-keyrepeat", vo.native_keyrepeat, 0),
     OPT_FLOATRANGE("panscan", vo.panscan, 0, 0.0, 1.0),
+    OPT_FLOATRANGE("video-zoom", vo.zoom, 0, -20.0, 20.0),
+    OPT_FLOATRANGE("video-pan-x", vo.pan_x, 0, -3.0, 3.0),
+    OPT_FLOATRANGE("video-pan-y", vo.pan_y, 0, -3.0, 3.0),
+    OPT_FLOATRANGE("video-align-x", vo.align_x, 0, -1.0, 1.0),
+    OPT_FLOATRANGE("video-align-y", vo.align_y, 0, -1.0, 1.0),
     OPT_FLAG("force-rgba-osd-rendering", force_rgba_osd, 0),
     OPT_CHOICE("colormatrix", requested_colorspace, 0,
                ({"auto", MP_CSP_AUTO},
diff --git a/mpvcore/options.h b/mpvcore/options.h
index 2ab9e517a0..1ff50688ce 100644
--- a/mpvcore/options.h
+++ b/mpvcore/options.h
@@ -19,6 +19,9 @@ typedef struct mp_vo_opts {
     int native_keyrepeat;
 
     float panscan;
+    float zoom;
+    float pan_x, pan_y;
+    float align_x, align_y;
 
     struct m_geometry geometry;
     struct m_geometry autofit;
diff --git a/video/out/vo.c b/video/out/vo.c
index be1ba84a12..1237ae0a23 100644
--- a/video/out/vo.c
+++ b/video/out/vo.c
@@ -488,13 +488,17 @@ static void clamp_size(int size, int *start, int *end)
 
 static void src_dst_split_scaling(int src_size, int dst_size,
                                   int scaled_src_size,
+                                  float zoom, float align, float pan,
                                   int *src_start, int *src_end,
                                   int *dst_start, int *dst_end,
                                   int *osd_margin_a, int *osd_margin_b)
 {
+    scaled_src_size += zoom * src_size;
+    align = (align + 1) / 2;
+
     *src_start = 0;
     *src_end = src_size;
-    *dst_start = (dst_size - scaled_src_size) / 2;
+    *dst_start = (dst_size - scaled_src_size) * align + pan * scaled_src_size;
     *dst_end = *dst_start + scaled_src_size;
 
     // Distance of screen frame to video
@@ -543,9 +547,11 @@ void vo_get_src_dst_rects(struct vo *vo, struct mp_rect *out_src,
         int scaled_width, scaled_height;
         aspect_calc_panscan(vo, &scaled_width, &scaled_height);
         src_dst_split_scaling(src_w, vo->dwidth, scaled_width,
+                              opts->zoom, opts->align_x, opts->pan_x,
                               &src.x0, &src.x1, &dst.x0, &dst.x1,
                               &osd.ml, &osd.mr);
         src_dst_split_scaling(src_h, vo->dheight, scaled_height,
+                              opts->zoom, opts->align_y, opts->pan_y,
                               &src.y0, &src.y1, &dst.y0, &dst.y1,
                               &osd.mt, &osd.mb);
     }